FIG. 68.--Bones of leg and foot of Phalanger. _ast_, Astragalus; _calc_, calcaneum; _cub_, cuboid; _ect.cun_, ecto-cuneiform; _ent.cun_, ento-cuneiform; _fb_, fibula; _mes.cun_, meso-cuneiform; _nav_, navicular; _tib_, tibia; _I-V_, first to fifth toes. (After Owen.) The second sub-family, PHASCOLARCTINAE (with the Koala only), is thus characterised:--Tail rudimentary; cheek-pouches present; superior incisors three, but only one premolar above and below; {140} caecum extraordinarily long; stomach with a cardiac gland; liver complicated by additional furrows, without a free caudate lobe; no azygos lobe to lungs; vaginal culs-de-sac free. The third sub-family, PHASCOLOMYINAE, contrasts with the others as follows:--Tail rudimentary; cheek-pouches present, but rudimentary; one incisor on each side above, but no additional premolars; all the teeth rootless; caecum not peculiar in shape; stomach with a cardiac gland; liver complicated by secondary furrows, without a free caudate lobe; lung with an azygos lobe; vaginal culs-de-sac free. The last sub-family, TARSIPEDINAE, is thus defined:--Tail long; tongue extensile; only one premolar; molars reduced; caecum absent. [Illustration] FIG. 69.--Vulpine Phalanger. _Trichosurus vulpecula._ x 1/6. SUB-FAM. 1. PHALANGERINAE.--The genus _Phalanger_ embraces five species, sometimes called by the generic name of _Cuscus_. They are largish animals with short ears; only the end of the tail is naked. Of these animals only one species is found in Australia itself, the rest inhabiting the islands lying to the north. The Spotted Cuscus, _Ph. maculatus_, is in spite of its vegetarian diet, and perhaps on account of its spots, spoken of as the "Tiger Cat." Mr. Aflalo remarks of it that though provided with a prehensile tail, it is little better as a climber than the tailless Koala. _Trichosurus_, including the "True Phalangers," includes largish species, which can be distinguished from the last genus by a chest-gland similar to that which occurs in _Myrmecobius_ and some other Marsupials of the present group. There are but two species, which are purely Australian. The "Brush-tailed Opossum," _T. vulpecula_ (perhaps better known as _Phalangista_ {141} _vulpina_), like its American pseudo-namesake (a true Opossum, genus _Didelphys_), "plays 'possum" on occasions. The dental formula is I 3/2 C 1/0 Pm 2/3 M 4/4. The ears are shortish. The Ring-tailed Phalangers, _Pseudochirus_, are more widely distributed than the last two genera; they range from Tasmania in the south to New Guinea in the north. They are not, however, ring-tailed, though the tip of the tail is generally white. As in the last genera, which have prehensile tails, the end of this appendage is naked. The mammae are four. The tooth formula is I 3/2 C 1/0 Pm 3/3 M 4/4. There are some ten species of the genus.